Subject: Geometry

# Words & Symbols In Geometry

## Geometry.WordsAndSymbols History

December 26, 2010 by bobdoleorama -
Changed line 92 from:
(:cellnr:)'+{$\begin{matrix}\rightarrow\\ AB \end{matrix}$}+'
to:
(:cellnr:)'+{$\overset{\rightarrow}{AB}$}+'
Changed line 94 from:
(:cell:){$\begin{matrix}\rightarrow\\ AB \end{matrix}$}
to:
(:cell:){$\overset{\rightarrow}{AB}$}
December 26, 2010 by bobdoleorama -
Changed line 124 from:
(:cell:){$\overrightarrow{AB} = \infty$}
to:
(:cell:){$\overleftrightarrow{AB} = \infty$}
December 26, 2010 by bobdoleorama -
Changed line 92 from:
(:cellnr:)'+{$\overrightarrow{ab}$}+'
to:
(:cellnr:)'+{$\begin{matrix}\rightarrow\\ AB \end{matrix}$}+'
Changed line 94 from:
(:cell:){$\overrightarrow{ab}$}
to:
(:cell:){$\begin{matrix}\rightarrow\\ AB \end{matrix}$}
Changed lines 102-104 from:
(:cell:)a – b = c &#8756; c + b = a
to:
(:cell:)a – b = c

&#8756; c + b = a
Changed line 114 from:
(:cellnr:)'+&#8776;+'
to:
(:cellnr:)'+{$\approx$}+'
Changed line 116 from:
(:cell:)a &#8776; x
to:
(:cell:)'+{$a \approx x$}+'
December 26, 2010 by bobdoleorama -
(:cellnr align=center bgcolor=#d4d7ba:)'''Symbol'''
(:cell align=center bgcolor=#d4d7ba:)'''Name'''
(:cell align=center bgcolor=#d4d7ba:)'''Example'''
(:cell align=center bgcolor=#d4d7ba:)'''Meaning'''
(:cellnr:)'+{$\Delta$}+'
(:cell:)Triangle
(:cell:)'+{$\Delta ABC$}+'
(:cell:)The triangle with points A, B and C.
(:cellnr:)'+{$\angle$}+'
(:cell:)Angle
(:cell:){$\angle A$}= 23°
(:cell:)Angle A is 23 degrees.
(:cellnr:)'+{$\overline{AB}$}+'
(:cell:)Line Segment
(:cell:){$\overline{AB}$} = 2.4 ft
(:cell:)The distance between points A and B is 2.4 feet.
(:cellnr:)'+{$\overrightarrow{ab}$}+'
(:cell:)Ray
(:cell:){$\overrightarrow{ab}$}
(:cell:)The line that begins at point A and continues through point B to infinity.
(:cellnr:)'+{$\overleftrightarrow{AB}$}+'
(:cell:)Line
(:cell:){$\overleftrightarrow{AB}$}
(:cell:)The infinite line that passes through or has points A and B.
(:cellnr:)'+&#8756;+'
(:cell:)Therefore
(:cell:)a – b = c &#8756; c + b = a
(:cell:)a minus b is c, therefore c plus b is equal to a.
(:cellnr:)'+< and >+'
(:cell:)Less/Greater Than
(:cell:)a < b
(:cell:)Length a is smaller than length b.
(:cellnr:)'+&#8804; and &#8805;+'
(:cell:)Less/Greater Than Or Equal To
(:cell:)a < b &#8805; c
(:cell:)a is smaller than b, b is larger than or equal to c.
(:cellnr:)'+&#8776;+'
(:cell:)Is Almost Equal To
(:cell:)a &#8776; x
(:cell:)The difference between a and x is negligible.
(:cellnr:)'+{$\perp$}+'
(:cell:)Perpendicular To
(:cell:){$AB \perp BC$}
(:cell:)Line AB is perpendicular to Line BC.
(:cellnr:)'+{$\infty$}+'
(:cell:)Infinity
(:cell:){$\overrightarrow{AB} = \infty$}
(:cell:)Line AB has infinite length.
(:cellnr:)'+r+'
(:cell:)r = 16.5
(:cell:)The radius is 16.5 units in length
(:cellnr:)'+d+'
(:cell:)Diameter
(:cell:)d = 50
(:cell:)The diameter is 50 units in length
(:cellnr:)'+&#8857;+'
(:cell:)Circle
(:cell:)&#8857;A<&#8857;B
(:cell:)Circle named A is smaller than Circle named B.
(:cellnr:)'+&#960;+'
(:cell:)Pi (Pronounced ‘pie’)
(:cell:)&#960; = C/D
(:cell:)Pi equals the circumference of a circle divided by that circles diameter.
(:cellnr:)'+{$\cong$}+'
(:cell:)Congruent To
(:cell:){$AB \cong BC$}
(:cell:)Lines AB and BC are of equal length, they are congruent to each other.
(:tableend:)
December 23, 2010 by bobdoleorama -
December 23, 2010 by bobdoleorama -
(:title Words & Symbols In Geometry:)

This section will serve as a basic introduction to some of the things you’ll see in geometry – you’ll no doubt have heard many of these terms and seen many of these symbols before, but it’s good to see what we’ll be using, and it’s handy to have a quick guide.

!!! A List of Words Used in Geometry

''(More in depth explanations and examples will be covered in subsequent pages!)''

(:cellnr bgcolor=#d4d7ba colspan=14 align=center:) '+'''The Breakdown'''+'
(:cellnr:)
*[[#t1 | Definitions for Points, Lines & Planes]]
*[[#t2 | Definitions for Angles]]
*[[#t3 | Definitions for Circles]]
*[[#t4 | Definitions for Other Geometric Words]]
*[[#t5 | Geometric Symbols]]
(:tableend:)

[[#t1]]
!!POINTS, LINES AND PLANES

:Line: In geometry, the definition of line must be more precise than our everyday use of the word because we also have to deal with rays and segments. A line may be straight or curved, and straight lines continue on past any points upon them. Lines are usually named after their two furthest points.
:Ray: A portion of a straight line that begins at a point and continues indefinitely.
:Segment: A portion of a straight line with two distinct endpoints, a line with finite length.
:Point: A symbol used to show position. Represented by a small dot or a letter.
:Endpoint: A point at one end of a segment, or the beginning of a ray.
:Midpoint: A point exactly halfway along a segment.
:Axis / Axes: A fixed, numbered reference line used in coordinate geometry.
:Origin: The point at which two or more axes meet in coordinate geometry.
:Vertex: The point where two straight lines, segments or rays meet creating an angle.
:Bisect: To bisect is to cross a line or segment at it’s midpoint.
:Plane: A two-dimensional form with length and width but no depth or thickness.
:Collinear: A set of two or more points is said to be collinear if they lie upon the same line.
:Congruent: Segments that have the same length are congruent.

\\
[[#t2]]
!!ANGLES

:Measure: A word used when talking about the value of an angle. An example might be “The measure of angle X is 120°”.
:Right Angle: An angle with a measure of exactly 90°.
:Perpendicular: Two lines are perpendicular if the angle which their intersection or meeting point forms is exactly 90°.
:Obtuse: An angle with measure greater than 90° and less than 180°.
:Acute: An angle with a measure of less than 90°.
:Adjacent Angles: Two angles are adjacent if they share the same vertex.
:Vertical Angles: Two non-adjacent angles formed by intersecting lines.
:Complementary: Angles whose combined total value add to exactly 90°.
:Supplementary: Angles whose combined total value add to exactly 180°.

\\
[[#t3]]
!!CIRCLES

:Chord: A straight line joining any two points on a circle.
:Secant: A straight line joining any two points on a circle and continuing beyond those points in both directions.
:Arc: A portion of the circumference of a circle between and including two points.
:Diameter: A chord that passes through the middle of the circle.
:Radius: The straight length or distance between the centre of a circle and a point on its circumference. The radius of a circle is exactly half of that circles diameter. The plural of radius is radii (pronounced ‘ray-dee-eye’).
:Circumference: The length around a circle.
:Semicircle: An arc measuring exactly half the circumference of a circle. Literally half a circle.
:Central Angle: An angle formed by two radii of the same circle (not two overlapping circles).
:Pi: A constant, irrational number derived from the ratio of the circumference of a circle to its diameter. Pi always has the same value, regardless of the size of a circle. This value has been calculated to many trillions of digits, but 3.141 is fine for our purposes.

\\
[[#t4]]
!!OTHER

:Parallelogram: An enclosed two-dimensional shape wherein all opposing sides are parallel.
:Polygon: An enclosed two-dimensional shape with a finite number of straight sides.
:Quadrilateral: A polygon with exactly four sides.

[[#t5]]
!! A TABLE OF GEOMETRIC SYMBOLS